Online-only shows, such as Netflix's House of Cards, are not legally covered
by BBFC ratings so the organisation is on a mission to persuade.

"That is the family silver for us," said Mark Dawson, chief digital officer for the British Board of Film Classification, as he discussed the way the organisation's ratings logos - 18, PG, U - have embedded themselves in public consciousness.

Everyone knows what the ratings mean, and according to the BBFC's research at least, almost everyone agrees with its assessment of what it is appropriate for young people to watch.

"We just implement the guidelines, which are set by public consultation," said Mr Dawson.

In cinemas and shops, the judgment of the BBFC's classifiers is protected by law. The 1984 Video Recordings Act and insists that it gives an age rating to all commercially distributed films.

At the time this meant cinema and video, and because of the way the law was written, it still does. The MPs of 1984, stirred by the "video nasty" furore, legislated without the benefit of technological clairvoyance. Their definitions were broad enough to cover DVDs or even films loaded on USB sticks, but not a world where digital downloads from iTunes, or streaming from Netflix or Amazon's LoveFilm are rapidly usurping "packaged media".

Mr Dawson's task is to make sure the BBFC's family silver maintains its value as the film industry migrates online.

Without statutory backup, his is a job of persuasion. He must persuade film companies and the big digital retailers and services to pay for their creations to be classified for online consumption (as well as cinema and DVD) and to show the BBFC rating and incorporate it into login controls so parents maintain their trust in the system.

Progress has been made. Some 250,000 films have now been been classified for online consumption and major players such as BT Vision and Netflix are using the ratings.

The BBFC is particularly pleased that Netflix submitted its hit Washington-based remake of House of Cards for classification. Made for the internet, and released as 13 episodes simultaneously last month, it was widely seen as the start of an important trend in entertainment. The BBFC gave all the episodes a 15 rating, except one, which featured a graphic suicide and got an 18.

"We're not about censorship and haven't been for a long time," said Mr Dawson. "We're about giving people the information they need."

Netflix will surely test that claim later this year when it debuts Hemlock Grove, another exclusive, created by Eli Roth. The director is best known as the founder of the "torture porn" genre with his sadistic 2006 horror film Hostel. Subsequent imitators 2009's Grotesque and 2011's Human Centipede 2, were both refused any classification.

Theoretically, if Netflix's adventure in original content produce something so distasteful the BBFC does not award a classification, it could simply go ahead and distribute it anyway.

"If self regulation doesn't work then there is the possibility of new legislation," said Mr Dawson, "it would take changing two words in the law."

He strongly emphasises, however, that the BBFC is not seeking and would not seek new powers to regulate internet firms and that the government supports its attempt to bring the online industry on board voluntarily.

To prove it can work, the BBFC needs to persuade Apple and Amazon, the dominant forces in internet film distribution, to use respect and display its ratings.